Question 208345
Well you just distribute the -5a^2.  So lets break it into parts<br>

-5a^2(-3a^4+2a^3+7)
=(-5a^2)(-3a^4)+(-5a^2)(2a^3)+(-5a^2)(7)
=(5*4)(a^2*a^4)+(-5*2)(a^2*a^3)+(-5*7)(a^2)<br>

Now just a note where when the you are multiplying to exponents and the bases are the same you add the exponents.  So this simplifies to<br>

=(5*4)(a^2*a^4)+(-5*2)(a^2*a^3)+(-5*7)(a^2)
= 20a^(2+4)-10a^(2+3)-35a^2
= 20a^6-10a^5-35a^2